For people not reading the whole thing (reasonable, it is long): the author comes to the conclusion that it was not so “genius” after all, given the prior art,

For people not reading the whole thing (reasonable, it is long): the author comes to the conclusion that it was not so “genius” after all, given the prior art, and that he read it in a computer graphics book. He still gives Carmack props for doing his homework and getting a working implementation built in a novel game engine.